Numerous methods and devices have been employed in the past for coating fasteners. Some of these methods and devices are useful in coating certain types of fasteners, but are not as versatile in coating other types of fasteners.
Examples of such methods and devices include U.S. Pat. No. 3,452,714 in the names of G.F.C. Burke, Richard J. Duffy et al.; U.S. Pat. No. 4,120,993 to Richard J. Duffy et al.; and U.S. Pat. No. RE 28,812 to Richard J. Duffy, one of the present inventors. The methods and devices disclosed in these United States Patents provide for the coating of fasteners in which the shank portion of the fastener depends below a pair of traveling belts. These fasteners are supported on the belts at their head portion. The methods and apparatus of the previously described patents do not provide the ability to precisely control the linear speed and rotation of the fasteners during the coating process. Also, it would be advantageous to provide a method and apparatus which would automatically and rapidly coat a wide variety of different fastener configurations and which may be adapted for use with a variety of different types of coatings.
It would also be advantageous to provide a method and apparatus which accommodates a variety of different fastener configurations and sizes and which could be quickly and easily adapted for coating such fasteners. In addition, it is desirable to provide a method and apparatus which has the versatility to coat a specified portion of the threads of the fastener, as well as the complete threaded area, and further, a method and apparatus which may coat only a specific portion of the radial distances about the threaded surface of the fastener. Furthermore, it would be advantageous to provide a method and apparatus which provides the ability to precisely control the linear speed and rotation of the fasteners to be processed.
The solutions to some of these problems have been disclosed in the application, Ser. No. 070,416, filed July 7, 1987, now U.S. Pat. No. 4,842,890, the disclosure of which is incorporated herein by reference. Improvements, however, are still desirable to increase the speed and efficiency of the apparatus and method, allow for faster and easier adaptation to fasteners of different configurations and sizes, create a smoother and more even coating of material, allow the use of different types of coating, and prevent clogging of the coating nozzle.